1. Field of the Invention
The present invention relates to a pressure compensation unit.
2. Description of Related Art
U.S. Pat. No. 5,661,244 relates to a pressure sensor which is used for measuring the pressure in a fuel tank. The pressure sensor includes a pressure supply line made of a metallic material, which is introduced into the pressure intake of a metal housing, where it is fixed in place by welding. The housing includes a flange section in the upper region, the flange section being connected to an outer wall of a tank, which represents the object to be measured, such that the pressure sensor is located on the inside of the tank. A porous filter, made from a fluoroplastic plastic, is disposed next to an atmospheric pressure intake. An adhesive tape is affixed at the atmospheric pressure intake in removable manner. The pressure sensor allows the safe operation and provides very high reliability for a sensor element with regard to the exclusion of air; there are also fewer restrictions with respect to the design of the sensor for small spaces, and it reliably avoids the entry of air and water or dust into the interior of the sensor.
Pressure-compensation components are installed inside a tank pressure sensor and compensate pressure differences between a reference space of the tank pressure sensor and the environment. The tank pressure is routed to the backside of a silicon diaphragm from below, while the pressure prevailing in the environment is acting as reference pressure from above, e.g., through an opening in the sensor housing, on the front side of the silicon diaphragm. A gas-permeable filter diaphragm is installed in a reference-pressure opening in order to protect the front side of the silicon diaphragm from water. The gas-permeable filter diaphragm acts as pressure-compensation element. The pressure-compensation element is usually water-repellent and impervious to fluids; it also seals the reference-pressure opening of the tank-pressure sensor of the tank installation unit from fluid. This design approach is meant to prevent the penetration of spray water and other fluid or solid media into the sensor space, regardless of the installation position of the pressure-compensation element.